#include <stdio.h>
#include <stdlib.h>

char ciur[1000001];
int euler[1000001];
int main()
{
    int n, i, j;
    FILE*fi,*fo;
    fi=fopen("fractii.in","r");
    fo=fopen("fractii.out","w");
    fscanf(fi,"%d", &n);
    for(i=1;i<=n;i++)
        euler[i]=i;
    ciur[0]=ciur[1]=1;
    for(i=2;i<=n;i++)
        if(ciur[i]==0){
            euler[i]=i-1;
            for(j=2*i;j<=n;j+=i){
                euler[j]=euler[j]*(i-1)/i;
                ciur[j]=1;
            }
        }
    long long sum=0;
    for(i=1;i<=n;i++)
        sum+=euler[i];
    fprintf(fo,"%lld", 2*sum-1);
    fclose(fi);
    fclose(fo);
    return 0;
}